Environment Minister Catherine McKenna and former prime minister Brian Mulroney will be in Montreal today to mark the 30th anniversary of a landmark treaty to protect the earth's ozone layer.

The Montreal Protocol was an international agreement signed in the city on Sept. 16, 1987 to phase out the use of chemicals being blamed for destroying the ozone layer.

Since it took effect in 1989, it has led to a drastic reduction in the production of chlorofluorocarbons, or CFCs, which were commonly found in products including refrigerators and aerosol sprays.

It has been revised on several occasions and currently has almost 200 signatories.

The Canadian government has hailed the agreement as a successful example of international co-operation and credited it with eliminating over 99 per cent of substances that were thinning the earth's protective layer.

Both McKenna and Mulroney, who was prime minister when the treaty was signed, are expected to speak at today's event.

An example of why climate change should not be a partisan issue.